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15 Cards in this Set
- Front
- Back
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describe directional selection
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moves avg phenotype in one direction or the other
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describe disruptive selection
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selection favors variants at each extreme
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describe stabilizing selection
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avg stay same, selection removes extreme variants
-reduces phenotype variation |
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describe bacterial resistance
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bacteria become resistance to anti-biotics over time
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describe sexual selection
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favors traits that increase reproductive success (at potential cost to survival)
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describe fitness
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contribution of genotype or phenotype to the genetic composition of subsequent generations relative to the contributions of other geno-/phenotypes
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problem between sexual and natural selection
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counter-acting forces
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two main mechanisms of evolution
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-gene flow (migration)
-genetic drift |
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two examples of genetic drift (and describe them)
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bottleneck: population decreases in size, random alleles survive (ex: northern elephant seal
founder: population colonizes new region, random which alleles follow (ex: Pitcairn Island) |
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4 main constraints on evolution
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-no genetic variation
-universal constraints -developmental process -cost vs benefit |
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what is sexual dimorphism
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dramatic differences between males and females
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describe developmental process
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evolutionary innovations are modifications of previously existing structures
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5 things that maintain genetic variation (describe each)
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-sexual reproduction (creates genetic variety)
-frequency-dependent selection (polymorphism) -environmental variation (environment favors certain phenotypes) -subpopulations (diff environmental factors leads to diff. selective pressure) -mutations (changes in DNA result in new allele varieties |
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disadvantages of sexual reproduction (3)
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-recombination can break up adaptive cominations
-reduces the rate genes are passed on -dividing offspring into genders reduces reproductive rate |
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describe polymorphism
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two or more clearly different phenotypes exist in same population of a species
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